The ultimate objective of this program is cure of children with leukemia. The program is a coordinated effort of therapy and study which includes: therapeutic trials aimed at prolonging leukemia-free survival with the more efficient use of conventional agents and the development of new agents; studies of the biology and pathogenesis of leukemia; and studies of the effects of leukemia and its therapy on normal tissues. The program consists of 11 interrelated projects: (1) primary therapy of acute lymphocytic leukemia; (2) primary therapy of acute nonlymphocytic leukemia; (3) therapy of relapse of leukemia; (4) leukemia cell kinetics; (5) studies of in vitro growth of normal and leukemic marrow; (6) neutrophil function and transfusion; (7) pathogenesis and therapy of pneumonia; (8) cardiac toxicity and function; (9) biochemistry of leukemic platelets; (10) pathogenesis of pancytopenia in mice; and (11) DNA and drug metabolite pools in leukemic cells. All involve patients with leukemia except project 10. All projects have the same ultimate objective and, though a wide variety of disciplines is involved, the organizational structure provides the means for a unified, coordinated effort.